The human vertebral column is a vital part of the human physiology that houses and protects the spinal cord, and provides structural support for the body. In a typical human, the vertebral column is made up of twenty-four articulating vertebrae and nine fused vertebrae, and is generally divided into several regions, including the cervical, thoracic, sacral, and coccygeal regions.
While variations exist between each vertebra depending on its location and region, vertebrae generally consist of a body, pedicles, a lamina, a spinous process, transverse processes, facet joints, and a spinal canal, each of which play a pivotal role in providing the overall supportive and protective functionality of the vertebral column. Of these features, the vertebral body is of particular importance in providing support. The vertebral body is the largest portion of the vertebra, provides an attachment point of intervertebral discs, protects the spinal cord, and bears the majority of the load of the vertebra.
Each vertebra is separated from an adjacent vertebra by an intervertebral disc, a cartilaginous joint that acts as a ligament to hold the vertebrae together. A disc consists of an outer annulus fibrosus which surrounds the inner nucleus pulposus. The annulus fibrosus consists of several layers of fibrocartilage which contain the nucleus pulposus and distribute pressure evenly across the disc. The nucleus pulposus contains loose fibers suspended in a mucoprotein gel. The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's daily activities and keeping the two vertebrae separated.
While the intervertebral disc protects adjacent vertebral bodies from impact or contact, various disorders may compromise the structure of the discs and negatively impact their functionality. For example, due to age, the nucleus pulposus may dehydrate and deform, or the annulus fibrosus may weaken and become more prone to tearing. Discs may also be damaged through trauma, resulting in undesirable bulging or loss of nucleus pulposus through a fissure. These disc disorders may diminish a disc's ability to absorb shock and transfer loads, or cause adjacent discs to contact, possibly resulting in acute or chronic pain for those suffering from these disorders.
Intervertebral disc disorders are frequently treated by removing portions of the disk or the entire disc and fusing adjacent vertebrae to prevent relative movement between the adjacent vertebrae. In other treatments, portions of the disc or the entire disc are removed and replaced with a prosthetic device. As these prostheses commonly replace diseased or damaged tissue, it is often necessary to surgically remove the existing tissue from the vertebra before implantation of the prostheses in order to clear away damaged tissue and to make room for the implant. Prosthetic procedures often involve mechanical prosthetics that replace the entire disc but do not provide the range of motion or stability of the natural healthy disc. Moreover, removal of all or part of the disc material can negatively impact the end plates of the vertebrae.
Current surgical techniques to repair intervertebral discs often involve invasive techniques that disturb otherwise healthy tissue adjacent the intervertebral disk. It would be desirable to treat diseased or damaged intervertebral discs by leaving the annulus fibrosus largely intact and undisturbed while restoring the stability and mobility of the native intervertebral disc.
Ideally, a tool to remove the tissue from within an intervertebral disc should be compatible with existing percutaneous surgical procedures, such that the tool is minimally invasive during insertion and use. The tool should also be adapted to adjustably access and remove tissue from a broad region of the intervertebral disc from a single insertion point, such that diseased tissue can be removed without requiring surgical insertion at multiple points and without requiring twisting or torquing that may undesirably damage healthy tissue. The tool should also perform several functions related to tissue removal, such that the number of tools that must be simultaneously inserted is reduced.